Forming rounded edges on blade-like elements



jam. 1?, 1956 s, J. STAPENELL.

FORMING ROUNDED EDGES ON BLADE-LIKE ELEMENTS Filed May 1', 1955 Sheets-Sheet l Jan- 17, 19 s. J. STAPENELL FORMING ROUNDED EDGES ON BLADE-LIKE ELEMENTS 3 Sheets-Sheet 2 Filed May 1, 1955 1956 s. J. STAPENELL 3 FORMING ROUNDED EDGES ON BLADE- LIKE ELEMENTS Filed May 1, 1953 I5 Sheets-Sheet 3 United States Patent FORMING ROUNDED EDGES 0N BLADE-LIKE ELEMENTS Samuel James Stapenell, Bristol, England, assignor to The Bristol Aeroplane Company Limited, Bristol, England, a British company Application May 1, 1953, Serial No. 352,507 Claims priority, application Great Britain Mays, 1952 Claims. (Cl. 51-144 This invention concerns a method and apparatus for forming rounded edges on blade-like elements byworking on the elementswith abrasive bands, belts or the ,like and relates more particularly to polishing the leading and trailing edges of a turbine or compressor blade. It is Anotherobject of the present invention is to provide a method and apparatus for rounding the edges of a blade-like element rapidly and cheaply and, if necessary, by mass-production methods.

According to the present invention a method of abrading the long edges of a blade-like element to round them comprises inserting the element lengthwise between a pair oftaut unsupported lengths of flexible abrading band, belt or the like, arranged with their abrading surfaces facing one another substantially parallel and spaced apart .by less than the minimum width of the element, and then rotating the element substantially about its long axis.

According to a feature of the present invention said blade-like element may be inserted between said lengths while they are held spaced apart by more than the overall thickness of the blade-like element.

In the case of a fiat, blade-like element the overall thickness is the true thickness of the element and in the case of a transversely curved element the overall thickness is the maximum distance from the convex surface to a line joining the long edges.

According to another feature of the present invention said lengths may be inserted between lengths which are portions of a single endless abrading band, or of a pair of endless abrading bands, and wherein said bandor bands are driven to move said lengths across the longedges of the blade-like element whileit is rotated. In this way a more rapid abrading action is obtained. While two separate bands, belts or the like may be used it is preferred that there is a single endless band or belt, two. unsupported lengths of which are arrangedas set forth above.

It is also preferred that the blade-like element be rotated first in one direction and then in the opposite diI'EC-r tion since it has been found that with the element rotating in one direction only there is a tendency to form a nonsymrnetrical radius at the edges being rounded. Preferably also, the width of said band or hands, belts, or the like is less than the length of the blade-like elementand the element is reciprocated substantially lengthwise while it is rotated. i

s According to another feature of the present invention apparatus for rounding the long edges of a blade-like Patented Jan. 17, 1956 element may comprise a system of pulleys to support an endless flexible abrading belt, band or the like so that a pair of unsupported lengths of the belt are drawn taut, have their abrading surfaces substantially parallel and facing one another and spaced apart by less than the minimum width of the blade-like element to be rounded a work holder mounted to rotate about an axis of rotation extending between said lengths of the belt and adapted to support a blade-like element extending length wise along said axis of rotation with its long edges lying one on either side of said axis of rotation, and means to rotate said holder. Since the space between the unsupported lengths of the abrading band, belt or the like is less than the minimum Width of the element, rotation of the latter will result in the unsupported lengths being displaced transversely so that the abrading band or belt is resiliently applied to the long edges of the element to round them. i r

It is preferred that, for automatic working of the apparatus, said lengths are spaced apart by more than the overall thickness of the blade-like element.

Preferably each of the unsupported lentghs of the band, belt or the like passes at one end over a jockey pulley which is spring urged against the belt to tauten the belt, and said jockey pulleys are adjustable mutuallyto incline their axes whereby the abrading surfaces of said lengths converge transversely thereof so as more easily to accommodate a tapering blade-like element, so that the bladelike element can be inserted between the lengths of band, belt or the like without first parting the bands.

In the preferred apparatus means is provided to drive said endless band and the work holder is rotated successively in opposite direction and means is provided to reciprocate said work holder substantially along said axis of rotation, thereby to reciprocate a blade-like element mounted in said work holder substantially lengthwise as it is rotated, the element being rotated in one direction during the instroke of its reciprocating movement, and in the other direction during the outstroke of its reciprocating movement.

One method and apparatus in accordance with the present invention will now be described by way of example with reference to the accompanying drawings which show a machine for rounding the leading and trailing edges of turbine and compressor blades.

In the drawings:

Figure 1 is a front elevation of the machine, certain parts having been omitted for the sake of clarity,

Figure 2 is a side elevation to a smaller size of the ma chine shown in Figure 1,

Figure 3 is a partial somewhat diagrammatic view to a larger size in the direction of arrow 3 in Figure 2,

Figure 4 is a somewhat diagrammatic partial view in the direction of arrow 4 to a larger size in Figure 1, and

Figures 5 and 6 are cross-sectional views to a larger size showing the details of construction of parts of the machine shown in Figures 1 and 2.

Referring to Figures 1 and 2 of the drawings the ma chine comprises a base unit generally indicated at 10 within which is mounted an electric motor 11. The motor 11 drives two pulleys 12 and 13 one at each end of the motor drive shaft 14 and outside the base unit 10. Mounted 011 top of the base unit 10 at one end thereof is a bearing housing 15 for a shaft 17 of a pulley 16. The pulley 16 is positioned above the pulley 13, and the shaft 17 is eccentrically adjustable in the housing 15 to facilitate the fitting and removal of the belt which is later described. The shaft 17 is adjustable after loosening the knurled nut 18.

Mounted on the bearing housing 15 are two upwardly inclined arms 20, 21 (see Figure 1) forming a V. Both arms are slotted longitudinally as at 23, and are bridged allow the arms 20, 21 and the having a T-slot 39 (see Figure '3). ries'a'lever 40, and a coiled tension spring 41 is connected between the free end of the lever 40 and the amuse? at their free ends by a horizontal strap 24 which has longitudinal slots 25 towards its ends. The arms 20, .21 are swingably mounted on the bearing housing each by means of a single bolt so that each arm is angularly adjustable with respect to the vertical.

A pulley wheel 26 is carried at the free end of each arm 20, 21 its shaft 27 passing through the slots 23 and 25 thereby fixing the strap 24 to the arms 20, 21. The slots 23 and pulleys 26 to be adjusted as desired. Y

A belt tensioning jockey unit 29 having a jockey pulley 31 is mounted in the slot 23 of each arm 20, 21 so that the pulleys 31 lie between the arms.

Each pulley 31 is' carried on a spindle 32 having a ball end 33 mounted in a spherical housing 34 formed in a two part block 35 carried at the end of an arm 36 hingeably connected at its other end by means of a bolt 37' to a plate 33 The arm 36 carplate-38 to urge the pulley 31 away from the arm on which it is carried. The units 29 are attached to their respective arm 20 or 21 by a bolt passing through the T-slot 39 in the unit and the slot '23 in the arm. In this manner the position of each pulley 31 is made adjustable.

An endless flexible felt belt 42, impregnated with abrasive material is positioned around the pulleys 13, 26 and 16 as shown in Figure 1. The run of the belt 42 follows a generally double V-shaped path, and the runs forming the inner V-shape pass over'the jockey A pulley 51 (see Figure 2) is driven from the pulley 12 by means of a belt 52, and the pulley 51 drives a shaft 54 on which is mounted a worm gear 55 which in turn drives a worm wheel 56 mounted on a shaft 57 also carrying at one end, outside the casing of the unit 50, a slotted thrower or crank 58. On the opposite end of the shaft 57 is carried a finger 59 (see also Figure 4) which is arranged to engage a number of equally circumferentially spaced pins 60 mounted on a freely rotatable timing. disc. 61 to turn the disc. The disc 61. carries a cam 62 on its peripheral edge, and the cam 62 is. arranged to engage a roller 63 carried at. the end of an arm 64 in turn carried for swing movement by the casing of a microswitch 66 mounted on the top of the base unit 10. When the disc turns to bring. the cam 62 against the roller 63, the arm 64 is moved, and

opens the microswitch 66 which acts through a relay to stop. the machine.

Fitted in the slot of the thrower 58 is a crank pin 70 Y which is adjustable along the slot to vary the throw of a rod 71 which is releasably and adjustably connected at its end remote from the pin70, as later described, to a I double arm 75 positioned generally vertically and having its lower end'hinged betweenthe limbs of a double arm, 76 projecting horizontally from the base unit 10. The'movement of the rod 71 is thereby imparted to, the arm 75 which is made long compared, with the length oftheblade so that the free end of the arm reciprocates substantially horizontally to and fro.

.Betweenthe limbs of the arm 75 and towards its free end is adjustably mounted in. elongated slots 82 a workhead having work-holder which is rotatably driven from shaft 54 by means of a'fiexible drive81. p I

The work-head contains an automatic reversing system for the work-holder '80. This will now be described. w Referring to; Figure: 5., the work-holder 80. is driven by a shaft carrying two bevel gears and The shaft 90 is axially slidable in the work-head to bring either the gear 91 or the gear 92 into driven engagement with a bevel gear 93 which isdriven from the flexible drive 81. Pivoted to the work-head casing as at 94 is a lever 95. The'lever passes through an aperture in the wall of ,the work-head casing and its inner end is forked to bridge-the shaft 90 and engage in a-circumferential groove 96 in;the shaft whereby movement of the lever shifts the shaft 90 axially to engage either the-gear 91 or 92. The outer endofthe lever 9.5.1 is restrained by a rod 98 (see Figure 2) connectedthereto and also slidable in a block 99 carried on the strap 24 midway between its ends. The" block 99 has a pair of screws 100 which are adjustable to vary the sliding friction ofthe-rod 98 in theblock 99. The arrangement is such that when the arm 75 is moving to the left in Figure 2 the lever 95 is held displaced to the right by the rod 98 which slides through the block 99, and the gear 92 is held in engagement with the gear 93 so that the work-holder 80 is rotated in one direction. When the arm. 75 commences to move to'the right in Figure 2, the

lever 9 5 moves to the left relatively to" the arm '75 so that the gear 92 is'disengaged with the gear 93 and the gear 91 brought into engagement therewith. The work holder 80 then rotates in the opposite direction, and as the arm'75 continues to move to the right the rod 98 slides back through the block 99 and holds the lever 95 displaced-to the left until the direction of movement of the arm 75 again changes. 7

It Willi be noted that the arm 75 reciprocates relatively slowly compared with the rotational speed of the work-holder 80-, and that the work-holder rotates in opposite directions during successive strokes of its "reciprocating movement. This ensures that the edges of the work piece are symmetrically rounded, there being a tendency to form a non-symmetrical radius if the work piece rotates always in the same direction;

As may be seen from Figure 5 a stop member 102 is pivoted to the top of the work head so that it is movable from an' inoperative position (shown in full lines) in which the lever 95 isfree to oscillate, to an inoperative position (shown inchain dotted lines) in which the lever 95 is held ina neutral position with both gears 91 and -92 disengaged with the gear 93. In this position of course the work holder remains stationary at least'in the rotational sense.

As previously stated the rod 71 is .releasably and adjustably connected to the arm 75. This is-necessary in orderthat the position of the work head in relation to the belt 42 may be varied as required, and also in'order that the arm 75 may be swung back for insertion and repivot 109 (see also- Figure 1), and is recessedso as to be a sliding fit over a reduced portion 110 of the sleeve 106, and thc' rod 71. A spring loaded plunger 111 is mounted on the block 108 and is arranged to pass'through the block so that it is normally engaged in a circumferential slot 112 in the .sleeve 106, thereby locking the sleeve. in the. block. When it is required to swing the arm'75 back toinsert or remove a work piecethe plunger 111 is lifted to free the block-108 from the sleevev 106 the block then being slid back along the rod 71 as the arm is moved. .I'n-Lorder to adjustthe distance of the work head from the belt 42 the screw 107 is loosened andthe sleeve 106 moved to the desired position.

'M'etal guards 113 are provided over the belt 42, and thetiming gear unit 50.

I'n' carrying out the methodusing-the machine just 7 described, the blade/whose long edges are to be rounded isQmogunted. in the work holder 80fwhic'h is fitted" with a suitable chuck to take the blade, with its long axis sub stantially horizontal and directed between the lengths 43 of the belt 42. The length of the stroke of the rod 71 is then adjusted at the thrower 58 so that the whole length of the long edges of the blade wll be reciprocated between the lengths 43, and the position of the blade in relation to the belt is adjusted by setting the sleeve 106 as previously described so that the blade will not be withdrawn from between the lengths 43. Thearms 2t), 21 and the jockey pulleys 31 are then adjusted so that the space between the lengths 43 is less than the minimum width of the blade, but greater than its overall thickness. This is preferred in automatic working since with the blade initially set with its width axis substantially vertical the blade can be moved freely to its position lying lengthwise between the lengths 43 of the belt without the necessity of having to part the lengths43 to insert the blade. If the blade is a tapered blade the spindles 32 are mutually inclined, after slacking oft'the screws 115 (see Figure 2) to loosen the ball-end 33 of each spindle 32 in its housing 34, so that the lengths 43 of the belt converge transversely to correspond with the blade taper. The spindles 32 are set in their new positions by retightening the screws 115. It is to be understood that it is not an essential feature that the spindles 32 be mutually inclinable. The lengths 43 could have their abrading surfaces parallel before a tapered blade is inserted between them, the blade then twisting the belt transversely to incline the abrading surfaces to conform with the long edges of the blade.

Next, the timing disc 61 is set so that it hasto make a complete revolution before the cam 62 operates the switch 66 and then the arm 75 is slid forward on the rod 71 and latched thereto so that the blade enters lengthwise between the length 43 of the belt. The motor 11 is then started, and the blade is rotated and reciprocated between the lengths 43 which are held taut and driven to pass over the long edges of the blade to round them. The operation automatically ceases when the disc 61 has been rotated by the finger 59 so that the cam 62 operates the switch 66 as previously described. The timing of the operation is dependent on the length of the finger 59 and the number of pins 60. These may be varied as desired. The felt belt is removed from time to time and impregnated with fresh abrasive material. The machine described is capable of rounding the long edges of turbine and compressor blades rapidly, cheaply, and with the necessary accuracy, and is therefore suitable in the mass production of such blades.

I claim:

1. Apparatus for rounding the leading and trailing edges of an aerofoil sectioned axial flow blade of the kind used in axial flow compressors and turbines, said apparatus comprising a base, a system of pulleys carried from said base, an endless abrading band of a width less than the length of a blade the leading and trailing edges of which are to be rounded, said band having an abrading surface and being supported by said pulley system with each of a pair of lengthwise portions of the band drawn taut between a pair of pulleys of said pulley system, said lengthwise portions being arranged substantially parallel with their abrading surfaces facing one another, and spaced apart by less than the minimum width of said blade a support means carried by said base, a work holder carried by said support means, means for rotating said work holder about an axis which passes between said lengthwise portions of the band, said work holder being adapted to support a blade, the leading and trailing edges of which are to be rounded, between said lengthwise portions of the band and lengthwise along said axis of rotation with the leading and trailing edges of the blade lying one on each side of said axis of rotation, means for moving said support means bodily to move said work holder repeatedly towards and away from said lengthwise portions of the endless band thereby to reciprocate a blade carried in said work holder substantially in the direction of its length, and reversing means for reversing the direction of rotation of said work holder each time its direction of bodily movement is reversed.

2. Apparatus as claimed in claim 1 wherein said pulley system includes a pair of jockey pulleys and each of said lengthwise portions of the abrading band passes at one end over one of the jockey pulleys which is spring urged against the band to tauten the band, and said jockey pulleys are adjustable mutually to incline their axes whereby the abrading surfaces of said lengths converge transversely thereof so as more easily to accommodate a tapering blade.

3. Apparatus as claimed in claim 1 wherein said support means comprises an arm, and said work holder is carried towards one end of said arm which is hinged toward its other end to said base, and a rod, connected at one end to a crank carried for rotation from said base, is releasably and pivotally coupled to the arm to oscillate said arm to and fro about its hinge along a small are thereby to move said work holder repeatedly towards and away from said lengthwise portions of the endless band.

4. Apparatus as claimed in claim 3 wherein said rod is releasably and pivotally coupled to said arm by means of a coupling comprising a sleeve on said rod, a block pivoted to said arm and recessed to receive said sleeve with the rod passing through said block, and a. spring loaded plunger carried by said block to be received in a recess in said sleeve thereby to releasably lock said sleeve in said block.

5. Apparatus as claimed in claim 4 wherein said sleeve is adjustable along said rod to vary the position of said work holder in relation to said endless band.

6. Apparatus as claimed in claim 3 wherein said work holder is mounted on a work head carried by said arm, and said work holder rotating means comprises a workholder driving shaft slidably journalled in said work-head, a pair of bevel gears mounted on said work holder driving shaft, a driven shaft journalled in said work head, a third bevel gear mounted on said driven shaft, said work holder driving shaft being slidable to engage either one of said pair of bevel gears with said third bevel gear, and said reversing means comprises a lever pivoted to said work head one end of said lever engaging said work holder driving shaft to shift the shaft axially when the lever is moved relatively to the work head, a friction device carried from said base, a rod slidable in said friction device,

said rod being pivotally connected to the other end of said lever and restraining said lever to hold said pair of bevel gears alternately in driving engagement with said third gear during successive strokes of the oscillating movement of said arm, said lever being moved by said rod relatively to said arm when the direction of movement of said arm changes, to disengage one of said pair of bevel gears, and engage the other, and thereby reverse the direction of rotation of said work holder.

7. Apparatus as claimed in claim 3 wherein timing means is provided to interrupt the operation of the apparatus after the completion of a predetermined number of reciprocations of the work holder, said timing means comprising a finger arranged to rotate with said crank, a freely rotatable disc adapted to be turned step-by-step by said finger, a cam surface on said disc, and a switch actuable by said cam surface to interrupt the operation of the apparatus after said disc has been turned through a selected angle.

8. A method of rounding the leading and trailing edges of an aerofoil sectioned axial flow blade of the kind used in axial flow compressors and turbines, which method comprises inserting the blade lengthwise between a pair of lengthwise running lengths of taut flexible abrading band arranged substantially parallel with their abrading surfaces facing one another and spaced apart by less than the minimum width of the blade, said lengths being '7 unsupported between their ends, and of a width less than ,the length of the blade, and then reciprocating the blade substantially lengthwise between said lengths of band and at the same'time rotating the blade in opposite direc tions about its long axis duringsuccessive strokes of its reciprocating movement,

. 9. A method of rounding the leading and trailing edges of an. aerofoil sectioned axial flow' blade of. the kindused in axial flow compressors and turbines, which method comprises inserting the blade lengthwisebetwcen a pair of lengthwise portions of a taut-flexible endless abrading band arranged substantially parallel with their abrading surfaces facing one another and spaced apart by lessxthan the minimum width of the blade, said lengthwise portions being unsupported between their ends, and the width of the band being less thanthe length of the blade, and then driving the band to move the band across the leading and trailing edges of the blade while at the same time reciprocating the blade substantially lengthwise and rotating the blade in opposite directions during successive strokes of its, reciprocating movement.

10. Apparatus, for rounding the leading and trailing edges of an aerofoil sectioned axial flow blade of the kind used in. axial flow compressors and turbines, said apparatus comprising a base, a system of pulleys carried from said base, an endless abrading band of a width less than the length of a blade the leading and trailing edges of whichare tot be rounded, said band: having an abrading surface and being supported by said pulley system with each of a pair of lengthwise portions'of the hand drawn taut between a pair of pulleys of said pulley system, saidlengthwise portions being arranged substantially parallel with their abrading surfaces facing one, another and spaced apart by less than the minimum width. of said blade, means for rotating a pulley of said pulley system to drive said endless band, a support means carried by said base, a work holder carried by said support means, means for rotating said work holder about an axis which passes between said lengthwise portions of the band, said work holder being adapted to support a blade, the'leading and trailing edges of which are to be rounded, between said len thwise portions of the band and lengthwise along said axis of rotation with the leading and trailing edges of the blade lying one on each side of said axis of rotation, means for moving said support means bodily to move said work holder repeatedly towards and away from said lengthwise portions of the endless band thereby to reciprocate a blade carried in said work holder substantially in the direction of its length, and reversing means for reversing the direction of rotation of said workholder each time its direction of bodily movement is reversed,

ltcferences Cited in the file o fthis patent UNITED STATES PATENTS 513,880 Clark et'al. Jan. 30, 1874 680,576 Ensign Aug. 13, 1901 909,544 Carney Jan. 12, 1909 996,443 Wysong June 27, 1911 1,986,745 Otlutt Jan. 1,1935

FGREIGN PATENTS 128,321 Germany Feb. 12, 1901 

